I am very happy to see this GUI wrapper, but it doesn't really suit my purposes. I have a laptop which is often asleep, and not always connected to my Firewire backup, so Cron is not something that really works for me. However, by running PSyncX I was able to get the proper syntax to create an applescript that does work for me. I decided to post it here in case anyone else might wish to modify it. Make sure that the source and destination folders are enclosed in both single and double brackets. Also, make sure that the second to last line (probably wrapped on your screen) is not wrapped.

set source_folder to "'UNIX Path to your source drive here'"
set dest_folder to "'UNIX Path to your destination drive here'"

Just to let you know, the /usr/local/bin/runpysnc script is only on people's computers if they have already installed PsyncX. That particular script checks to see if your hard drive is actually connected to the computer before running /usr/local/bin/psync

So this tip won't work unless people either A) replace runpsync with psync in your instructions or B) download and install PsyncX first.